Expandible key



Aug. 18, 1964 R. A. BLQM 3,145,036

EXPANDIBLE KEY Filed Dec. 26, 1962 Z? X Z? ,6 26 5 INVENTOR. IPOYABLOM TQ A4Q%$H ATTORNEY United States Patent 3,145,036 EXPANBHELE KEY Roy A. Elem, Massapequa Park, N.Y., assignor to Fetter instrument (Company, Inn, Piainview, ND)! a corporation of New York Filed L ce. 26, 1962, Ser. No. 2d7,l02 d Qlaims. (Ci. 287-45205) This invention relates to a keying arrangement for keying together a shaft and a hub having matching, rectangular axially extending key-ways cut therein.

In many applications as, for example, in high speed tape transports, a hub must be secured to a shaft for conjoint rotation. The use of keys inserted within keyways cut in both the hub and the shaft is an economical arrangement. However, when the application requires oscillatory motion, the shaft and the hub must be keyed together with no play upon reversal of direction or" movement. In such instances, the usual keys cannot be employed since play between the shaft and the hub cannot be eliminated under normal manufacturing techniques.

For this reason, other types of arrangements have been utilized which, however, lack the advantages of economy of assembly and ease of disassembly of the keyed units.

It is, therefore, an object of the present invention to provide an improved keying arrangement for keying together a shaft and a hub having matching rectangular axially extending key-ways cut therein.

It is a further object of this invention to provide an improved keying arrangement in which the key may be expanded laterally to engage the side walls of key-ways and an assembled shaft and hub thereby to reduce play therebetween.

Other objects and advantages will be pointed out here-- inafter in the description of this invention which may best be understood by reference to the accompanying drawing, in which the single figure is a partially sectioned view of an assembly utilizing the keying arrangement of the present invention.

In the figure, there is shown a shaft having a hub 12 mounted thereon. The shaft 10 is provided with a rectangular, axially extending key-Way 14 cut therein. Similarly, the hub 12 is provided with an axially extending rectangular key-way 16 matching the key-way in shaft 10.

A key 1% is inserted within the rectangular area defined by the matclnng key-ways. The key 18 is provided with a first V-shaped axially extending slot 20 cut into the key face 22 adjacent the hub 12 and a second V-shaped axially extending slot 24 cut into the key face 26 adjacent the shaft 143.

First and second wedges 28 and 30, respectively, are inserted into the respective first and second slots 2% and 24. The wedges extend beyond the slotted faces 22 and 26 of the key.

Means are provided to urge each wedge into its respective slot to expand the key laterally into tight engage- 'ice inent with the sides of the key-ways 14 and 16. The urging means may conveniently be provided by a set screw 32 threadably engaged into aperture 34 in the hub 12.

in order to reduce angular deflection of the side Walls of the key, it is desirable to out each slot so that the outer wall thereof, is parallel with the side wall of the key-Way. Further, to reduce localized stress concentration, it is desi able to increase the radius at the apex of the slot as by drilling holes 36 and 37 through the key-way at the apex.

The key lit is constructed preferably of metal having the requisite hardness for the application intended. The wedges may be metal, but are often preferably formed of a tough, slippery plastic such as polytetrafluoroethylene, which is commercially available under the DuPont trade- Tefion, for example.

This invention may be variously modified and embodied within the scope of the subjoined claims.

What is claimed is:

l. A keying arrangement for keying together a shaft and a hub having matching, axially extending key-Ways cut therein, comprising,

a key dimensioned to fit into the rectangular area defined by the aligned key-ways,

said key having a first axially extending V-shaped slot cut in the key face adjacent said hub and having a second axially extending V-shaped slot cut into the key face adjacent said shaft,

said first and second slots being olfset from each other and extending into the key to a depth so that the lower end of one slot is past the lower end of the other,

a first and second wedge respectively inserted into said first and second slots,

said wedges extending above the slotted faces of the key, and

means urging said wedges into their respective slots to expand the key into tight engagement with the sides of the key-ways.

2. A keying arrangement in accordance with claim 1 in which said wedges are formed of polytetrafiuoroethylene.

3. A keying arrangement in accordance with claim 1 in which said urging means comprises a set screw threadably engaged in said hub.

4. A keying arrangement in accordance with claim 1 in which the apex of each slot is provided with an enlarged radius to prevent localized stress concentration.

References Cited in the file of this patent UNITED STATES PATENTS 224,103 Morse Feb. 3, 1880 1,435,811 Cuntala .r Nov. 14, 1922 1,612,769 OConnell Dec. 28, 1926 2,807,485 Seibert Sept. 24, 1957 2,937,042 Wilder May 17, 1960 

1. A KEYING ARRANGEMENT FOR KEYING TOGETHER A SHAFT AND A HUB HAVING MATCHING, AXIALLY EXTENDING KEY-WAYS CUT THEREIN, COMPRISING, A KEY DIMENSIONED TO FIT INTO THE RECTANGULAR AREA DEFINED BY THE ALIGNED KEY-WAYS, SAID KEY HAVING A FIRST AXIALLY EXTENDING V-SHAPED SLOT CUT IN THE KEY FACE ADJACENT SAID HUB AND HAVING A SECOND AXIALLY EXTENDING V-SHAPED SLOT CUT INTO THE KEY FACE ADJACENT SAID SHAFT, SAID FIRST AND SECOND SLOTS BEING OFFSET FROM EACH OTHER AND EXTENDING INTO THE KEY TO A DEPTH SO THAT THE LOWER END OF ONE SLOT IS PAST THE LOWER END OF THE OTHER, A FIRST AND SECOND WEDGE RESPECTIVELY INSERTED INTO SAID FIRST AND SECOND SLOTS, SAID WEDGES EXTENDING ABOVE THE SLOTTED FACES OF THE KEY, AND MEANS URGING SAID WEDGES INTO THEIR RESPECTIVE SLOTS TO EXPAND THE KEY INTO TIGHT ENGAGEMENT WITH THE SIDES OF THE KEY-WAYS. 